The present invention relates generally to interconnect devices for electronic components. More particularly, the present invention relates to a flexible interconnect cable design suitable for use in very high frequency applications.
Many telecommunication and data communication systems support very high speed data and/or clock rates. For example, many practical digital communication systems process data at speeds of up to 40 Gigabits/second (xe2x80x9cGbpsxe2x80x9d), and the fiber optics telecommunication industry (and other technology sectors) continue to develop communication systems capable of handling even faster data rates. Practical high speed data communication systems employ a number of interconnected elements such as electronic devices, components, modules, circuit boards, subassemblies, and the like. High speed clock/data inputs and outputs of such elements must be interconnected at the subsystem and system levels.
The prior art contains a limited number of interconnect solutions suitable for use at very high speeds (e.g., 40 Gbps and higher). For example, single-ended threaded microwave connectors and microwave interconnect cabling is often utilized between integrated circuit packages, electronic components, and optical modules. Such connectors, however, require cumbersome cable layouts, require large specialized component packages, and preclude the use of differential signaling (which provides a number of advantages such as common mode immunity). In an effort to eliminate bulky connectors and cabling altogether, recent industry proposals have centered around complex interconnections between the integrated circuit substrate and the optics module substrate, where such interconnections utilize various wire bonding and specialized signal launch techniques (an approach requiring intimate device co-location and precise package alignment).
Very high speed integrated circuit chips are often manufactured in the form of a flip chip die having a number of high speed inputs and outputs. A common interconnect technique employs a circuit substrate (such as a ball grid array substrate) upon which the flip chip die is mounted. The circuit substrate includes multiple conductive layers separated by insulating layers and conductive vias that form an interconnect structure for both high speed and low speed signals; the circuit substrate itself is then mounted to a circuit board or card. The substrate acts as an interposer, redistributes signals from the fine pitch chip solder bumps to the BGA solder balls, and provides coefficient of thermal expansion matching. The design of the high speed signal interconnects in the circuit substrate can be complex and time consuming, resulting in added manufacturing costs. In addition, such circuit substrates must be custom designed to accommodate the physical and electrical characteristics of the flip chip die and/or the physical and electrical characteristics of the subassembly circuit board/card.
A flexible electrical interconnect cable according to the present invention facilitates high speed signal transmission between electrical devices, components, modules, circuit boards, and the like. The interconnect cable provides a relatively low cost solution for high speed applications that support data rates of 40 Gbps (and higher). The interconnect cable may also be integrated with a circuit substrate in a manner that eliminates the need to design high speed interconnects within the circuit substrate, e.g., the printed circuit board.
The above and other aspects of the present invention may be carried out in one form by an electrical interconnect cable comprising a flexible dielectric layer and a flexible conductive layer coupled to the flexible dielectric layer, where the flexible conductive layer includes a number of conductive traces of a high-frequency electrical transmission line structure.